In a large saucepan, add butter, bittersweet and unsweetened chocolate. Place over low heat and stir until smooth. Remove from the heat - whisk in sugar, vanilla, espresso powder and salt. Whisk in eggs, one at a time, until combined. Stir in flour. Add nuts and fold in just until combined. Scoop the mixture into a 9" x 13" baking pan coated with nonstick spray - bake until a toothpick placed into the center comes out with moist crumbs attached, about 25 to 30 minutes. Remove and place baking pan on a wire rack to cool completely.

To make the frosting

In a large mixing bowl, beat peanut butter and butter until combined. Add confectioners' sugar, salt, and nutmeg, mixing until combined. Mix in milk and vanilla. Scoop the mixture on top of the brownies and spread to an even layer with an off-set spatula.

To prepare the topping

In a small skillet, add butter and chocolate - heat and stir over low until melted and smooth. Pour over the peanut butter layer and spread smooth with an off-set spatula. Place into the refrigerator and chill until set, about an hour and a half, before cutting into bars to serve.Just found the recipe? Click here to see where we talked about it!

Miriam - It is debatable. I've used it before in recipes like this, but I used regular peanut butter for this and it worked quite well. I can't say for sure though if it would be fine in this specific recipe, but I don't see why it wouldn't.

Thanks, Joe. I only ask because I know in certain recipes like peanut butter cookies, it really makes a difference. Otherwise, the oil will separate. Since the peanut butter topping will not be baked, it makes sense that it would be ok.